Use target to determine uclibc / glibc. Fix CFI related bug. 

Merginf the CFI patch in or1k-src will cause .eh_frame to be generated on crtstuff which is not wanted. This patch will prevent this behavior.

This patch changes two critical default values:

1)
-muclibc is only default if the target is or1k*-linux-uclibc (e.g. or1k-linux-uclibc)
-mglibc is the default for or1k*-linux-*

2)
crt0.o will not be used for linking. Use crt1.o instead (defined in gnu-user.h) when building for linux targets.
This will require a separate patch for uClibc which I will submit.